Bottled water is becoming more and more popular, but the peculiar smell of PET bottled drinking water has gradually attracted the attention of consumers. Although it will not affect hygiene and health, it still needs sufficient attention from manufacturing enterprises, logistics and sales terminal enterprises. PET bottled water consists of water, a PET bottle and a plastic cap. Water, colorless and odorless, with a little peculiar smell dissolved in it, will produce unpleasant taste when drinking.
PET bottles are made from food-grade PET. PET material, scientific name is polyethylene terephthalate, colorless, tasteless at room temperature, widely used in beverage, food, edible oil field. Plastic cover, usually made of food-grade HDPE. The scientific name is high-density polyethylene, which is colorless and odorless at room temperature. It is widely used in the fields of beverages, food and edible oils.
So, where does the peculiar smell in water come from? After a lot of research and testing, people have come to the general conclusion that the peculiar smell of water is mainly from the packaging materials in addition to the residual factors of bottle washing disinfectant, mainly in:
1.The own taste of the packaging material
Although the packaging material is odorless at room temperature, when the temperature is higher than 38°C for a long time, the small molecular substances in the packaging material are easy to volatilize the odor and migrate to the water, resulting in an odor. PET material and HDPE material composed of macromolecules are very sensitive to temperature. Generally, the higher the temperature, the greater the odor. Because part of the medium and low molecular substances remain in the macromolecule, its volatilized odor is greater than that of the macromolecule at high temperature. Avoid transportation and storage under high temperature conditions, effectively avoiding the generation of odors.
Under the irradiation of ultraviolet rays, some low-molecular-weight substances will be decomposed, resulting in odor. The packaging material has been added with anti-ultraviolet substances, but under the condition of exposure, there are some residual group substances at the end of the medium and low molecular chain in the polymer, which can be easily activated and produce a small amount of degradation products, which dissolve in water and produce odor. If you add high temperature, the odor will be more obvious. Should avoid direct sunlight, transport and store at suitable temperature, can effectively avoid the generation of odor.
2. Degradation of additives in bottle cap raw materials
The main purpose of adding lubricant is to improve the opening performance of the bottle cap and make it easier for consumers to drink; adding a release agent to smoothly release the mold when making the cap; adding color masterbatch to change the color of the cap and diversify the appearance of the product. These additives usually contain unsaturated fatty amides, in which the double bond C=C structure is easily oxidized. If exposed to UV light, high temperature and ozone, this double bond can be opened to form a mixture of degradation: saturated and unsaturated fatty acids, acetaldehyde, carboxylic acids and hydroxides, etc., which dissolve very easily in water and produce different tastes and odor.
Selecting additives that match the production process can effectively avoid the generation of volatile and odorous mixtures. The lubricant Sincera developed by the GRACE company in the United States can not degrade under the conditions of ultraviolet rays, ozone and high temperature. It has been commercialized in European and American markets.
3. Odor residue from the lid making process
Additives such as lubricants are added to the materials used for making the cover. The lid making process includes heating and high-speed mechanical stirring. Odors due to processing remain in the lid and eventually migrate into the water.
There are usually two processes for making caps: injection molding and compression molding.
Injection molding process: cover with Injection Molding Machine, which belongs to the traditional way. Additives must be used. The temperature is between 240°C and 280°C. At high temperature, the material will undergo some chemical changes and produce peculiar smell.
Compression molding process: The use of compression molding mechanism to cover is a new technology that has appeared in recent years. It can be used without additives (except color masterbatch), and the processing temperature is controlled at 160 ° C - 170 ° C, which will not cause chemical changes to the material. The effective way to reduce the peculiar smell of the lid is to use as few additives as possible in the material and reduce the processing temperature. Many international well-known companies use the compression molding process to make lids, and they think this is an effective and good method.
4. Odor residue caused by air pressure system
Humidity, microbial content, oil concentration, and solid particles determine the quality of compressed air. The traditional air compression system cannot completely eliminate the pollution of oil and other impurities during the working process, so it will also cause the bottled water to produce peculiar smell; with the air compression system With the development of micro-oil and oil-free technology, clean compressed air is the choice to ensure quality and quality in many bottled water and beverage production processes.
